'http://www.devhut.net/2010/06/22/vba-converting-between-decimal-and-binary/
'Decimal To Binary
' =================
' Source: http://groups.google.ca/group/comp.lang.visual.basic/browse_thread/thread/28affecddaca98b4/979c5e918fad7e63
' Author: Randy Birch (MVP Visual Basic)
' NOTE: You can limit the size of the returned
'              answer by specifying the number of bits
Function Dec2Bin(ByVal DecimalIn As Variant, _
              Optional NumberOfBits As Variant) As String
    Dec2Bin = ""
    DecimalIn = Int(CDec(DecimalIn))
    Do While DecimalIn <> 0
        Dec2Bin = Format$(DecimalIn - 2 * Int(DecimalIn / 2)) & Dec2Bin
        DecimalIn = Int(DecimalIn / 2)
    Loop
    If Not IsMissing(NumberOfBits) Then
       If Len(Dec2Bin) > NumberOfBits Then
          Dec2Bin = "Error - Number exceeds specified bit size"
       Else
          Dec2Bin = Right$(String$(NumberOfBits, _
                    "0") & Dec2Bin, NumberOfBits)
       End If
    End If
End Function
 
'Binary To Decimal
' =================
Function Bin2Dec(BinaryString As String) As Variant
    Dim X As Integer
    For X = 0 To Len(BinaryString) - 1
        Bin2Dec = CDec(Bin2Dec) + Val(Mid(BinaryString, _
                  Len(BinaryString) - X, 1)) * 2 ^ X
    Next
End Function

Sub TestDecBin()
    MsgBox Dec2Bin(45) & " = " & Bin2Dec(Dec2Bin(45))
End Sub